The first GPS unit that lets you send text messages is supposed to be coming out July 31. It’s the “Earthmate PN-60w” from Delorme.com. (Catchy title, eh?)

Messages are conveyed via satellite and are not dependent on cell phone coverage, so you can send them even in the deepest darkest jungle. The PN-60w is ruggedized and waterproof, in case you are in one of those movies where you fall into the river and are swept downstream over the rapids.

Users can send messages to email addresses, cell phones, buddy lists, and social networking sites like Twitter, Facebook, Fire Eagle, SpotAdventures.com, or Geocaching.com, complete with GPS coordinates. (Help! I’m floating downstream on the Amazon.) The map coordinates will help, even if they change as you move along.

The device comes with North America GPS, topographic maps and street coverage for the U.S. and Canada. Nautical charts, aerial images, natural resource maps, and other locations, are available by subscription. This “”save me,” or “I am here” device does not come cheap: you can pre-order it for $550 at Amazon.com.